在c++代码中完成对xz压缩包的解压

要在C代码中完成对xz压缩包的解压，可以使用liblzma库。以下是一个示例程序：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <lzma.h>

#define BUFFER_SIZE 1024

int main(int argc, char *argv[]) {
    if (argc != 3) {
        printf("Usage: %s <input_file> <output_file>\n", argv[0]);
        return 1;
    }

    // Open the input file
    FILE *input_file = fopen(argv[1], "rb");
    if (input_file == NULL) {
        printf("Error: Failed to open input file %s\n", argv[1]);
        return 1;
    }

    // Open the output file
    FILE *output_file = fopen(argv[2], "wb");
    if (output_file == NULL) {
        printf("Error: Failed to open output file %s\n", argv[2]);
        fclose(input_file);
        return 1;
    }

    // Initialize the decoder
    lzma_stream stream = LZMA_STREAM_INIT;
    lzma_ret ret = lzma_stream_decoder(&stream, UINT64_MAX, 0);
    if (ret != LZMA_OK) {
        printf("Error: Failed to initialize decoder (%d)\n", ret);
        fclose(input_file);
        fclose(output_file);
        return 1;
    }

    // Allocate input and output buffers
    uint8_t *in_buf = malloc(BUFFER_SIZE);
    uint8_t *out_buf = malloc(BUFFER_SIZE);
    if (in_buf == NULL || out_buf == NULL) {
        printf("Error: Failed to allocate input or output buffer\n");
        fclose(input_file);
        fclose(output_file);
        return 1;
    }

    // Process the input stream
    size_t in_pos = 0;
    size_t out_pos = 0;
    while (1) {
        // Read from the input file
        size_t in_size = fread(in_buf + in_pos, 1, BUFFER_SIZE - in_pos, input_file);
        if (in_size == 0 && feof(input_file)) {
            break;
        }

        // Update the input position
        in_pos += in_size;

        // Decode the input buffer
        stream.avail_in = in_pos;
        stream.next_in = in_buf;
        stream.avail_out = BUFFER_SIZE - out_pos;
        stream.next_out = out_buf + out_pos;
        ret = lzma_code(&stream, LZMA_RUN);
        if (ret != LZMA_OK && ret != LZMA_STREAM_END) {
            printf("Error: Failed to decode input (%d)\n", ret);
            fclose(input_file);
            fclose(output_file);
            return 1;
        }

        // Update the input and output positions
        in_pos = stream.avail_in;
        out_pos = BUFFER_SIZE - stream.avail_out;

        // Write to the output file
        if (fwrite(out_buf, 1, out_pos, output_file) != out_pos) {
            printf("Error: Failed to write to output file\n");
            fclose(input_file);
            fclose(output_file);
            return 1;
        }

        // Move any remaining data to the start of the input buffer
        if (in_pos > 0 && in_pos < BUFFER_SIZE) {
            memmove(in_buf, in_buf + in_pos, in_pos);
        }
    }

    // Flush the decoder
    while (1) {
        stream.avail_in = 0;
        stream.next_in = NULL;
        stream.avail_out = BUFFER_SIZE - out_pos;
        stream.next_out = out_buf + out_pos;
        ret = lzma_code(&stream, LZMA_FINISH);
        if (ret == LZMA_OK || ret == LZMA_STREAM_END) {
            out_pos = BUFFER_SIZE - stream.avail_out;
            if (fwrite(out_buf, 1, out_pos, output_file) != out_pos) {
                printf("Error: Failed to write to output file\n");
                fclose(input_file);
                fclose(output_file);
                return 1;
            }
            break;
        }
        if (ret != LZMA_OK && ret != LZMA_STREAM_END) {
            printf("Error: Failed to flush decoder (%d)\n", ret);
            fclose(input_file);
            fclose(output_file);
            return 1;
        }
        out_pos = BUFFER_SIZE - stream.avail_out;
        if (fwrite(out_buf, 1, out_pos, output_file) != out_pos) {
            printf("Error: Failed to write to output file\n");
            fclose(input_file);
            fclose(output_file);
            return 1;
        }
    }

    // Free the input and output buffers
    free(in_buf);
    free(out_buf);

    // Close the input and output files
    fclose(input_file);
    fclose(output_file);

    return 0;
}

该程序首先打开输入和输出文件，然后初始化解码器。接下来，它循环读取输入文件，并将数据传递给解码器进行解压缩。解压缩后的数据被写入输出文件。最后，程序释放内存并关闭文件。

要编译该程序，需要链接liblzma库。例如，可以使用以下命令：

gcc -o xz_decompress xz_decompress.c -llzma

该命令将生成名为“xz_decompress”的可执行文件。要将一个名为“input.xz”的xz压缩包解压到一个名为“output”的文件中，可以执行以下命令：

./xz_decompress input.xz output